Q 2: minamata disease Flashcards
Mercury (Hg)
Heavy metal • Exists in several forms: elemental mercury (Hg0), inorganic mercury and organic mercury • Hg0 commonly called quicksilver • Highly toxic to most forms of life
what is its state under normal conditions
Hg - mercury
sources of mercury
Geologic deposits – Often found as an ore (HgS) – High affinity to coal • Weathering of rock • Volcanic eruptions erosion
Side Story: The Almadén Mine
World’s largest deposit called the Almadén
deposit, found in Spain
• Spanish convicts and North African slaves worked
the mine in the 1500-1600s
other sources from human- (anthropogenic)
fossil fuel (46%), metal production (, 10% artisinal and small scale gold production, cement production, waste incineration, dental amalgam
how is hg moved through enviro
biogeochemical cycle- (wind water
what is the most dangerous form
organic- bound to carbon
toxicity
Specific to chemical form – Organic vs inorganic • Also depends on: – Route of exposure – Dose – Age of person exposed (fetus most susceptible) – Duration of exposure – Health of person exposed • We are going to focus on organic mercury – Specifically, METHYLMERCURY [CH3Hg-X]
organic means
carbon
Methylmercury (MeHg) Profile- metabolism/ biotransformation and elimination
– Slowly demethylated in intestines and liver- 95% absorbed
• Elimination
– Major routes include bile and feces
Absorption
of hg
– Inhalation: vapours of MeHg absorbed
– Oral: highly absorbed in GI tract (approximately 95%)
– Dermal: slow absorption, especially compared to
dimethylmercury**
how is methyl merc ditributed in the body
– Distributed throughout body, but especially brain and
fetus
Karen Wetterhahn
Side story: Karen Wetterhahn (dimethylmercury poisoning) • 48 year old woman who passed away 10 months after coming in contact with an unknown amount of dimethylmercury • Karen was a prof at Dartmouth College who specialized in toxic metals • Was using (CH3)2Hg as a reference material, spilled a few drops on her glove • Started experiencing symptoms 3 months later – Blood Hg levels 80x the toxic threshold
Bioaccumulates:
concentrations in organism
increase over time
Biomagnifies:
concentrations increase up the
food web to higher trophic levels
– Carnivorous fish (freshwater pike, marine sharks,
swordfish) can have Hg tissue concentrations as much
as 10 000 – 100 000 times the concentration of the
water they reside in!)
Cross both the blood-brain barrier and bloodplacental
barrier
MINAMATA DISEASE:
A social, environmental, economic,
and political story- WHO
Chisso Corporation Ltd.
– Acetaldehyde plant (MeHg as
a byproduct)
• Inorganic mercury (mercury
salts) used as a catalyst to produce acetaldehyde
through the hydration of acetylene
• This began in 1932 and continued until 1968
• Minamata disease officially discovered in 1956
when was minimata desease discovered
1956
“Dancing Cat Syndrome”
One of the first indications that something was going on in Minamata • Excessive salivation, violent movements, death • Famous “H.I. fluid” experiments conducted on cats by Dr. Hosokawa (lifetime employee and later superintendant at the Chisso hospital
Timeline of Events cont.
of minamata
1956: The official discovery of Minamata started with two young girls (ages 3 and 5) who exhibited strange symptoms, including: – Clumsiness – Disorientation – Difficulty speaking – Convulsions • This was just the beginning…
Victims of Postnatal Minamata Disease
Early patients diagnosed as having Minamata disease died very quickly (acute/subacute exposure) • Clinical symptoms common to most patients included: – Paraesthesia (mouth/hands/feet) – Sensory/auditory disturbances – Constriction of the visual field (concentric) – Deafness – Dysarthria – Ataxia/Tremors Many victims of Minamata Disease were babies born to pregnant women eating contaminated fish • Mothers may or may not have exhibited any symptoms • Clinical manifestations included: – Delayed achievement of development milestones • Speech and motor function – Severe cerebral impairment (cerebral palsy and mental retardation)
Overview of Timeline of Events
Early 1950s – Fish, birds, cats* • 1956: Minamata Disease officially discovered – Study Group for Minamata Disease established • 1959: Organic mercury determined to be the cause • 1965: MeHg poisoning occurred in Niigata, Japan – Different acetaldehyde plant • 1968: Japanese government announced its opinion that Minamata Disease was indeed caused by consumption of fish contaminated with methylmercury discharged from the chemical plants… thanks guys
summary of minamata
Methylmercury poisoning event in the 1950- 1960s
• Occurred in Minamata, Japan
– A fishing and farming village
• Cause?
– Chisso Corporation Ltd.
• Number of “official”/certified cases? (as of the
year 2001)
– 2955 (1700 of which died)
• Number of “unofficial”/suspected cases?
– 200 000
Relief for Minamata Victims?
- Compensation Agreement (1973)
– Lump sum of money (medical expenses, pension)
– However, have to be certified as officially having Minamata Disease - Political Settlement (1995)
– Many people were denied official status, led to lawsuits, conflict, etc.
– Under this new settlement, people experiencing peripheral limp
sensory disturbances were entitled to receive a lump sum as well - Judicial Damage Compensation (2004)
– Another lawsuit led to more Minamata victims (who did not fall under
the original “victim” criteria) being entitled to compensation - Additional Measures
– Better health benefits for those who had already received their lump
sum
in summary- clean up
• Chisso Corporation/the Japanese government
was responsible to:
– Clean up the environment! (Reclamation of Minamata
Bay and surrounding area)
– Environmental monitoring
• Victim compensation (as previously mentioned)
TOTAL COST: 144 BILLION YEN, or
1.4 BILLION CAD
ontario
– Wabigoon-English River
System contaminated with Hg
discharged from Dryden Chemicals Ltd
Iraq
– Consumption of methylmercury-contaminated bread
higher hg in which fish
– Fish highest in Hg include shark, swordfish, king mackerel,
tilefish from Gulf of Mexico (FDA)
– Ex. FDA #s: salmon (2µg/4 ounces) vs. swordfish (147µg/4
ounces)
